The present invention relates to a door switch for turning ON/OFF a contact as interlocked with the door opening and closing action and, more particularly to, a door switch used for a door provided at a doorway of a guard such as a protection fence or wall installed so as to surround a variety of machines.
A variety of machines such as machine tools, semiconductor manufacturing equipment and food processing machines are typically surrounded by a guard such as a protection fence or wall. The operator is prevented from inadvertently coming in contact with those machines in operation by the guard. A doorway of such a guard is provided with a door for permitting the operator to enter for inspection and repair of the machines.
A door switch is equipped to such a door for turning OFF the contact in interlocked with the door opening and closing action to thereby cut off power for those machines.
Accordingly, when the operator opens the door, the machines are stopped in operation. Then the operator can enter the guard safely for inspection and repair thereof.
A prior art door switch will be described with reference to FIGS. 6 and 7. A guard is provided with a door 3. The door 3 can be opened and closed in an arrow direction between an opened position indicated by a solid line and a closed position indicated by a two-dots-and-dash line.
The door switch comprises a switch body 2 and a door key 7. The switch body 2 includes a built-in switch contact for turning ON/OFF power for the machine and also has a door key insertion hole 5.
The switch body 2 is attached to the guard 1 with its door key insertion hole 5 as oriented toward a door 3. The door key 7 is provided to the door 3 in such a manner that it can be inserted into the door key insertion hole 5 when the door 3 is opened or closed.
When the door 3 is closed with the door key 7 as inserted into the door key insertion hole 5, the switch contact in the switch body 2 is in a power application state for the machines, in which they are in operation.
When the door 3 is opened by the operator, the door key 7 is pulled out of the door key insertion hole 5. Then, the switch contact in the switch body 2 is switched to a state for cutting off power for the machines to stop them in operation.
Such a door key 7 is always protruded toward the door key insertion hole 5 irrespective of whether the door 3 is opened or closed. The operator is liable to come in contact with the door key 7 when he opens the door 3 to come into or go out of the guard 1.
Accordingly, it is a main object of the present invention to provide a door switch that its switch contact is turned OFF when the door is opened and also that its door key is not protruded out the inside of the door.
The above and other objects, advantages, and features of the invention will be more apparent from the following description.
A door switch according to the invention operates interlocked with the door opening and closing action and comprises a switch body and a key unit used as separated from the switch body, wherein the switch body includes a switch case having a door key insertion hole therein and a switch contact built in the switch case and the key unit includes a unit case, a door key which is provided in the unit case in such a manner that it can be protruded out and retreated into it, for switching the switch contact when inserted into the door key insertion hole, and a door key drive mechanism for, when pressed from the outside, protruding the door key from the unit case and, when released from the pressing, retreating the door key into the unit case.
In the invention, preferably, the switch body is attached on one side of the door or a structure to which that door is mounted and the key unit, on the other side thereof.